園藝作物田間雜草之危害及管理

鍾維榮 邱建中

台中區農業改良場

摘 要

園藝作物包括果樹、蔬菜、花卉及景觀作物，作物種類繁多，栽培方式複雜。在園藝作物生產上，雜草是重要的限制因子。雜草不僅影響園藝作物的產量，亦降低園藝產品的品質。一般而言，園藝作物之栽培與管理機械化程度低，田間雜草防治大都仰賴人工除草及中耕培土。園藝作物殺草劑之開發與使用較農藝作物為慢，主要原因為園藝作物種類多，栽培面積小，廠商缺乏興趣來申請及開發。但殺草劑在將來園藝作物生產上將扮演重要角色。本文將分別概述主要園藝作物雜草防治方法及所使用的殺草劑。蔬菜作物屬短期及勞力密集作物，一般行株距小，栽培密度高，幼苗纖細且生長緩慢，植株軟弱而根部淺，最易受雜草競爭為害而減產。雜草引起蔬菜減產方面，一般平均達22 ~ 30 %之間，但對直播類而生長緩慢的蔬菜，其減產影響可達90 ~ 100 %。蔬菜田雜草發生情形與一般旱田相同，大多為一年生雜草。在使用化學藥劑來防治雜草時需考慮蔬菜的種類、栽培方法、雜草種類及數量來決定殺草劑的種類及用法。一般蔬菜作物對殺草劑抵抗性弱，噴施時必須防範藥害的發生。蔬菜田所使用殺草劑必須在土壤中殘效性較短，不影響後期作物，萌前處理葉面噴施為佳，藥劑用量較少，藥效穩定，選擇性高，不致發生藥害情形。在噴施時需注意下列事項：單位面積藥劑用量要正確，注意覆土及整地工作，考慮噴施時氣候及土壤條件，藥劑對後作影響，適當噴施方法及時期。在新植果園，雜草直接與幼樹競爭土壤中之水分、養分與二氧化碳以及光線。雜草可減少50 %以上幼樹生長量。在成年果園之雜草競爭較不嚴重，但仍顯著的降低果樹產量及品質。果園雜草防治特性是在於抑制雜草生長，而非全面殺死，在某些方面要考慮雜草在水土保持的功能。果園草生管理在果樹生長與收穫量是一主要因素。在果園草生栽培理念下，保持果園適當雜草生長。一個果園完整的雜草防治計畫包括：中耕、割草、覆蓋與施用殺草劑等方法。果園草相變化劇烈及迅速。如只防除一年生雜草，則多年生雜草將成為優勢雜草，但如大量防除多年生草，果園土壤有流失之虞。果樹株型高大，根部深，對殺草劑耐性較強。果園所使用殺草劑一般藥效較強，殘性較久，使用量較多，以萌後型殺草劑居多，在各種果樹共同使用的殺草劑種類很多。在果園使用殺草劑時須考慮下列事項：噴藥時間、雜草種類、推薦藥劑特性、果樹品種及生長時期、採收日期、灌溉方法、雨量情形等。大部份藥劑不可直接噴及果樹，幼樹施用量要減少。花卉作物依生長習性可分為一、二年生草花、多年生宿根或球根花卉、木本及觀賞花卉作物等；在花卉田雜草防治上，必須瞭解各種花卉作物之生長習性及栽培方式。目前大部份花卉仍依賴人工除草，配合中耕除草，但利用殺草劑來防除花卉田雜草是將來的趨勢。一、二年生草花種子非常細小，幼苗非常軟弱，對殺草劑非常敏感，無任何推薦藥劑。球根類花卉比一、二年生草花對殺草劑的耐藥性較強，可使用萌前殺草劑，具短期或中等殘效性，不會影響後期作物。在切花生產上，露地栽培花卉之雜草防治可使用萌前殺草劑，溫室栽培花卉之雜草防治依作物種類及栽培方法而異。花木類一般根深、莖幹木質化，可使用土壤移動小，殘效性較強的殺草劑。大部份觀賞花木皆種植於盆栽，使用的殺草劑必須為較不具溶於水的特性，能吸附於盆栽介質來延長殘效期。目前本省在園藝作物推薦的殺草劑，在蔬菜作物，計有十七種，使用於十三種蔬菜。其中以甘藍田推薦十種藥劑最多，西瓜與番茄各推薦四種藥劑，洋蔥與大蒜各推薦三種藥劑。在果樹作物計推薦十七種殺草劑於十二種果樹作物，其中以柑桔園推薦十二種藥劑為最多，其次為鳳梨園推薦六種藥劑，香蕉與葡萄各推薦四種及二種藥劑。在藥劑上，嘉磷塞推薦於九種果樹上。在花卉作物僅推薦一種混合藥劑於杜鵑花苗圃。在園藝作物生產上，利用殺草劑防治雜草日漸重要。但在無推薦藥劑下，農民自行參考使用各類殺草劑，藥害情形時有所聞，造成農民及農政單位不少困擾。建議本省農業試驗單位針對較重要園藝作物篩選適當的殺草劑來防治園藝作物田間雜草，推薦予農民使用。

關鍵詞：園藝作物、雜草防治、殺草劑。

Weed Control and Damage in Horticultural Crop

Chung, Wei-Jong and Chen-Chung Chiu

Taichung District Agricultural Improvem

Abstract

Horticultural crops included fruit tress, vegetable crops, flower and ornamental crops that have vary species and complicated cultural methods. In the production of horticultural crops, weed is the limiting factor, it not only decrease the yield, also reduce the produce quality. The development and marketing of herbicides recom- mended in horticultural crops is slower than that of agronomy crops due to small- scale growing areas. The weed control methods and registered herbicides in the horti- cultural crops were discussed.

The characteristics of vegetable crops is labor intensive, high population densi- ty, narrow spacing, short growing season, fragile seedling and plant that often caused great yield loss due to its weak competivity with weeds. Manual weeding and herbi- cides application is the common weed control methods in the production of vegetable crops. The herbicides used in vegetable crops should have the following characters: high selectivity, pre-emergence type, short residual period, lower dosage.

The newly planted fruit trees is more sensitive to weed competition than old orchard. The weed control in orchard is rather to inhibit the weed growth than to eliminate them in the sense of water and soil conservation. A completed weed management program in orchard should include cultivation, mulching, mowing and chemical method. Weed control in orchard by herbicides is become more popular. The herbicide recommended in orchard weed control should have the following prop- erties: post-emergence type, long residual period, broad effectiveness. The following factors should take into account when use herbicide in the orchard: application timing, weed species, chemical nature, fruit trees variety, tree age, harvesting date, rainfall and irrigation method.

Weed problem in flower crops is less important and less significant than fruit trees and vegetable crops in term of yield loss. Manual weeding and cultivation is the major weed control method in the production of flower crops. Herbicides that regis- tered in flower crops is mostly applied on ornamental crops. The commercial produc- tion of cut-flower and bulb crops is lacking of appropriate herbicide to control the weed in flower field.

There are 17 herbicides recommended on 13 vegetable crops, in which 10 herbi- cides have registered in cabbage field. There are 16 herbicides recommended on 12 fruit trees, in which 11 herbicide have used in citrus orchard. Only one chemical have recommended on azalea nursery. Weed control in the production of horticultur- al crops will become more important in the future due to the problem of labor short- age and high wage in agricultural sector. Development and testing of effective and specific herbicides used in the production of horticultural crops should be enhanced and promoted.

Key word: Horticultural crops, Weed control, Herbicide